Spinal fusion implant

ABSTRACT

An improved prosthetic implant for forming a rigid structure between adjoining vertebrae in a spinal column. The prosthetic implant includes a cage having a top, bottom, front end, back end, first side and second side walls. The first side wall has an arcuate surface. The top and bottom wall include one or more ridges to engage a surface of an adjacent vertebrae. The top and bottom wall also include an opening to receive packing material such as medicine, human tissue and the like. The top and bottom walls also incline simultaneously in two directions.

[0001] This application claims priority on my co-pending U.S.Provisional Application Ser. No. 60/121,705, filed Feb. 25, 1999entitled “Spinal Fusion Implant.”

[0002] The present invention pertains to prosthetic implants and moreparticularly to inner body spinal prosthetic implants to fuse two ormore vertebrae together.

INCORPORATION BY REFERENCE

[0003] U.S. Provisional Application Ser. No. 60/121,705, filed Feb. 25,1999 entitled “Spinal Fusion Implant” is incorporated by reference.

BACKGROUND OF THE INVENTION

[0004] The human spine is made up of a column of thirty-three bones andtheir adjoining structures. The vertebrae near the head are known as thepresaccral vertebrae which are separate bones capable of individualmovement. The bodies of these vertebrae are connected by anterior andposterior ligaments and by disks of fibrocartilage generally known asintervertebral disks. These disks are positioned between opposite facesof adjacent vertebral bodies. This column of vertebrae andintervertebral disks form a central axis that supports the head andtorso. These vertebrae also enclose an opening through which the spinalcord passes therebetween.

[0005] The presaccral vertebrae are normally held in position to oneanother by the intervertebral disks, ligaments and musculature of thebody. These vertebrae move relative to adjacent vertebrae thuspermitting the head to be turned relative the body and providing a widerange of flexibility to the spine.

[0006] One of the most costly health problems to society involves backpain and pathology of the spine. These problems can affect individualsof all ages and can result in great suffering to victims. Back pain canbe caused by several factors such as congenital deformities, traumaticinjuries, degenerative changes to the spine and the like. Such changescan cause painful excessive motion, or collapse of a motion segmentresulting in the contraction of the spinal canal and compresses theneural structures causing debilitating pain, paralysis or both which inturn can result in nerve root compression or spinal stenosis.

[0007] Nerve conduction disorders can also be associated with invertibledisks or the vertebrae themselves. One such condition is herniation ofthe intervertebral disk, in which a small amount of tissue protrudesfrom the sides of the disk into the foramen to compress the spinal cord.A second common condition involves the development of small bone spurs,termed osteophytes, along the posterior surface of the vertebral body,again impinging on the spinal cord.

[0008] Upon identification of these abnormalities, surgery may berequired to correct the problem. For those problems associated with theformation of osteophytes or herniations of the intervertebral disk, onesuch surgical procedure is intervertebral diskectomy. In this procedure,the involved vertebrae are exposed and the intervertebral disk isremoved, thus removing the offending tissue, or providing access for theremoval of the bone osteophytes. A second procedure, termed a spinalfusion, may then be required to fix the vertebrae together to preventmovement and maintain a space originally occupied by the intervertebraldisk. Although this procedure may result in some minor loss andflexibility in the spine, due to the relatively large number ofvertebrae, the minor loss of mobility is typically acceptable.

[0009] During a spinal fusion following a diskectomy, a prostheticimplant or spinal implant is inserted into the intervertebral space.This prosthetic implant is often a bone graft removed from anotherportion of the patient's body, termed an autograph. The use of bonetaken from the patient's body has the important advantage of avoidingrejection of the implant, but has several shortcomings. There is alwaysa risk in opening a second surgical site in obtaining the implant, whichcan lead to infection or pain for the patient, and the site of theimplant is weakened by the removal of bony material. The bone implantmay not be perfectly shaped and placed, leading to slippage orabsorption of the implant, or failure of the implant to fuse with thevertebrae.

[0010] Other options for a graft source of the implant are bone removedfrom cadavers, termed allograft, or from other species, termed axenograft. In these cases while there is the benefit of not having asecond surgical site as a possible source of infection or pain, there isincreased difficulty of the graft rejection and the risk of transmittingcommunicable diseases.

[0011] An alternative approach is using a bone graft or to use amanufactured implant made of a synthetic material that is biologicallycompatible with the body and the vertebrae. Several compositions andgeometries of such implants have been utilized, ranging from simpleblocks of material to carefully shaped implants, with varying success.

[0012] There has been an extensive number of attempts in developing anacceptable prosthetic implant that can be used to replace anintervertebral disk and yet maintain the stability of the intervertebraldisk spaced between adjacent vertebrae, at least until completearthrodesis is achieved. These prosthetic implants have taken manyforms. While many types of synthetic prosthetic devices have beenproposed, the success ratio has been low and the surgical procedureshave been complicated and often traumatic to the patient.

[0013] One of the more prevailing designs of these prosthetic implantstakes form of a cylindrical implant. These types of prosthetic implantsare represented by Brantigan U.S. Pat. No. 4,878,915 and Ray U.S. Pat.No. 4,961,740. In these cylindrical implants, the exterior portion ofthe cylinder can be threaded to facilitate insertion of the prostheticdevice. Some of these prosthetic implants are designed to be poundedinto the intervertebral disk space and the vertebral end plates. Thesetypes of devices are represented in Brantigan U.S. Pat. No. 4,834,757and Brantigan U.S. Pat. No. 5,192,327. The Brantigan and Ray patents alldisclose prosthetic implants wherein the transverse cross-section of theimplant is constant throughout the length of the implant and istypically in the form of a right circular cylinder.

[0014] Other prosthetic implants have been developed that do not have aconstant cross-section. For instance, the patent to McKinna U.S. Pat.No. 4,714,469 shows a hemispherical implant with elongated protuberancesthat project into the vertebral end plate. The implant of Bagby U.S.Pat. No. 4,934,848 is in the form of a sphere which is positionedbetween the centrums of the adjacent vertebrae.

[0015] The various prosthetic implants can be generally divided into twobasic categories, namely, solid implants and implants that are designedto encourage bone ingrowth. Solid implants are represented by U.S. Pat.Nos. 4,878,915 and 4,349,921. The remaining patents discussed aboveinclude some aspect that permits bone to grow across the implant. It hasbeen found that devices which promote natural bone ingrowth achieve amore rapid and stable arthrodesis. These implants are typically filledwith autologous bone prior to insertion into the intervertebral diskspace. These implants typically include apertures which communicate withopenings in the implant, thereby providing a path for tissue growthbetween the vertebral end plate and the bone or bone substitute withinthe implant. In preparing the intervertebral disk space for a prostheticimplant, the end plates of the vertebrae are preferably reduced tobleeding bone to facilitate tissue growth within the implant.

[0016] A number of difficulties still remain with the many prostheticimplants currently available. While it is recognized that hollowimplants which permit bone ingrowth in the bone or bone substitutewithin the implant is an optimum technique for achieving fusion, most ofthese devices have difficulty achieving this fusion, at least withoutthe aid of some additional stabilizing device, such as a rod or plate.Moreover, some of these devices are not structurally strong enough tosupport the heavy loads applied at the most frequently fused vertebrallevels, mainly those in the lower lumbar spine.

[0017] There has been a need for providing a prosthetic implant thatoptimizes the bone ingrowth capabilities and strong enough to supportthe vertebrae until arthrodesis occurs. There is a further need for suchan implant that is capable of maintaining or restoring the normal spinalanatomy at the instrumented segment. There is also a need for an implantthat exhibits reduced slippage when inserted between vertebrae anddiminishes the occurrence of nerve pinching.

SUMMARY OF THE INVENTION

[0018] The present invention pertains to an improved implant and moreparticularly to an improved prosthetic implant used to facilitate in thefusion of two or more vertebrae.

[0019] In accordance with the principal feature of the presentinvention, there is provided a prosthetic implant that is formed of abiologically compatible material for use in humans. The prostheticimplant is shaped and sized for insertion between two vertebrae. In onespecific embodiment, the prosthetic implant is designed to be placed inthe intervertebral disk space that was formerly occupied by anintervertebral disk. The intervertebral disk is partially or completelyremoved prior to insertion of the prosthetic implant between thevertebrae. In one specific embodiment, the shape and size of the cage isselected to have an anatomically correct shape. In another embodiment,the prosthetic implant is shaped to increase the area of contact withthe vertebrae and/or to closely emulate the region formerly occupied bythe intervertebral disk. In still another embodiment, the prostheticimplant is designed to be readily inserted by established surgicalprocedures, with minimal chances of surgical difficulty. In yet anotherembodiment, the geometry of the implant ensures proper load bearing,desired load bearing and support through the fused vertebrae minimizingthe likelihood of the prosthetic implant dislocating relative to thevertebrae either during surgery or during the post operative fusingprocess.

[0020] In accordance with another aspect of the present invention, thereis provided a prosthetic implant which includes a cage having a topwall, a bottom wall, a front end wall, a back end wall, a first sidewall, and a second side wall. In one embodiment, the cage is made of amaterial that is inert or biologically compatible with the vertebrae.The material of the cage includes, but is not limited to, bone,stainless steal, titanium, chrome, cobalt, polycarbonate, polypropelene,polyethylene, polymethylmethacrylate, polysolfone types filled withglass and/or carbon fibers, and various types of carbon and fiberreinforced polymers. In accordance with another embodiment, the cage isdesigned to maintain a tension load of about ten to forty pounds andmore preferably about fifteen to thirty-five pounds on the disk tissue.This tension load facilitates in maintaining the cage in positionbetween the vertebrae and accelerates bone ingrowth between thevertebrae. In still another embodiment, the cage is made of a materialwhich closely approximates the elasticity of the vertebra. In still yetanother embodiment, the cage is coated with and/or made up of materialwhich is radiolucent to enhance the visibility of the implant whenexposed to X-rays.

[0021] In accordance with still another aspect of the present invention,the first side wall and second side wall of the cage of the prostheticimplant extends substantially along the longitudinal axis of the cageand wherein the two side walls are configured to enhance the stabilityof the cage within the intervertebral disk space. In one embodiment, thefirst and/or second side wall is at least partially arcuate. In anotherembodiment, the first and second side wall have different faceconfigurations. In one specific embodiment, the first side includes anarcuate surface and the second side has a substantially flat or planarsurface. In one specific embodiment, the first side wall has asubstantially uniform arcuate surface. In another specific embodiment,the actuate surface has a radius of curvature of about 2 to 30 degrees.In cage configurations having an arcuate first side wall surface, thecage is positioned in the intervertebral disk space such that thesubstantially flat or planar surface of the second side is positionedclosely adjacent to the spinal cord and the first side is positionedadjacent the peripheral edge of the intervertebral disk space.Prosthetic implant cages having an arcuate or curvilinear side wall havebeen found to more closely conform to the surfaces with theintervertebral disk space thereby resulting in a higher degree ofsuccess for fusing together two vertebrae. The different sideconfigurations of the cage also function as a visual aid to ensure thatthe cage is properly oriented between two vertebrae.

[0022] In accordance with yet another aspect of the present invention,the cage of the prosthetic implant includes a top wall and/or bottomwall having at least one rigid surface adapted to engage the undersidesurface of a vertebrae within the intervertebral disk space. The ridgeis designed to secure or bite into the vertebrae surface. In oneembodiment, the top wall includes a plurality of ridged surfaces. Inanother embodiment, the bottom wall includes a plurality of ridgedsurfaces. The ridged surfaces on the top and/or bottom wall can have anumber of configurations. In one specific embodiment, the ridges havediamond shaped surfaces, thereby functioning similar to teeth-likestructures. In another specific embodiment, the ridge is a uniformstructure extending over the lateral and/or longitudinal surface of thetop and/or bottom wall. In another embodiment, the ridges are positionedon the top end and/or bottom wall and are spaced from the outerperipheral edge of the bottom and/or top wall. In still anotherembodiment, the top and bottom wall have similar ridge configurationsand a similar number of ridges; however, it can be appreciated that thetop and bottom wall can have different numbers and/or differentconfigurations of ridges. In still yet another embodiment, the ridges inthe top and/or bottom wall of the cage anchor the cage in between thevertebrae and provide channels for bone ingrowth which facilitates inthe fusion of the vertebrae.

[0023] In accordance with still yet another aspect of the presentinvention, the cage of the prosthetic implant includes one or moreopenings in one or more of the walls of the cage. In one embodiment, theopenings are designed to receive materials which facilitate in thefusion of the vertebrae, facilitate in the positioning of the cagebetween the vertebrae, and/or secure the cage in place within theintervertebral disk space. In one specific embodiment, one or more ofthe openings are designed to receive a packing material whichfacilitates in the formation of a graft between two vertebrae. Suchpacking material can include, but is not limited to, medicine, humantissue, animal tissue, synthetic tissue, human cells, animal cells,synthetic cells, and the like. In another specific embodiment, the cageincludes a plurality of openings to allow blood supply to grow from thesides of the cage to the vertebrae between the cage. In still anotherspecific embodiment, one or more openings in the cage are filled with apacking material which includes one or more components that are selectedto grow out of the openings of the cage radially, longitudinally and/orvertically from the cage and grow into the bone tissue of the adjoiningadjacent vertebrae. In still another specific embodiment, one or moreopenings are filled with bone material or a synthetic material, with orwithout a bone activating matter such as hydroxyapatite bone or phallicprotein, bone growth factor, or cartilage activation factor. In yetanother embodiment, the top and/or bottom wall of the cage have anopening which communicates with an internal cavity of the cage. In stillyet another embodiment, the top and bottom walls include at least oneopening that are substantially the same shape and size. In accordancewith another embodiment, the first side wall, second side wall, frontend wall and/or back end wall include at least one opening adapted toreceive an instrument for guiding and/or inserting the cage between thevertebrae of the spine by an anterior, posterior, lateral and/orlatroscopic approach into the spinal column. The openings allow asurgeon to select which approach is best for inserting the prostheticimplant in the intervertebral disk space. In one specific embodiment,the instrument opening includes a securing mechanism, such as, but notlimited to, a thread, in the opening to secure the instrument within theopening.

[0024] In accordance with another aspect of the present invention, atleast one or more edges of the cage are rounded off so as not to besharp. The rounding off of the edges reduces and/or eliminates pinchingof the nerve leading from the spinal cord which can result in pain,damage or paralysis to the individual. The rounded edges avoid orminimize nerve pressure that can be exerted on the nervesintervertebrally exiting the spinal cord. The one or more rounded offedges also facilitates with the insertion of the cage within theintervertebral disk space. In one specific embodiment, the lateral edgesof the cage are rounded off. In another specific embodiment, all theedges of the cage are rounded off.

[0025] In accordance with still another aspect of the present invention,the top wall and/or bottom wall are at least partially inclined alongthe longitudinal axis of the cage. In one embodiment, the top walland/or bottom wall are uniformly inclined from the back end wall to thefront end wall. In one specific embodiment, the back end wall is higherthan the front end wall. In another specific embodiment, the angle ofinclination of the top and/or bottom wall is about 0.5 to 15 degrees andpreferably about 1 to 10 degrees and more preferably about 3 to 8degrees. The inclination of the top and/or bottom wall of the cagefacilitates in the ease of insertion into the vertebrae column and/orprovides a better fit for the cage within the intervertebral disk spacesince the inclination better matches the anatomical shape of the spacebetween the vertebrae of the spinal column. In accordance with anotherembodiment, the inclined top and/or bottom wall of the cage accommodatethe positioning of the cage between two vertebrae of the spinal columnand the ridges on the top and/or bottom wall of the cage are adapted tocontact the surfaces of the vertebrae bone and secure the cage inposition between the vertebrae until the fusion of the vertebrae iscomplete.

[0026] In accordance with yet another aspect of the present invention,the top wall and/or bottom wall are at least partially inclined betweenthe first and second side wall of the cage. In one embodiment, the topwall and/or bottom wall are uniformly inclined from the first and secondside wall. In one specific embodiment, the second side wall is higherthan the first side wall. In another specific embodiment, the angle ofinclination of the top and/or bottom wall is about 0.5 to 15 degrees andpreferably about 1 to 10 degrees and more preferably about 3 to 8degrees. The inclination of the top and/or bottom wall of the cagefacilitates in the ease of insertion into the vertebrae column and/orprovides a better fit for the cage within the intervertebral disk spacesince the inclination better matches the anatomical shape of the spacebetween the vertebrae of the spinal column.

[0027] In accordance with another aspect of the present invention, apair of cages are used to support and/or fuse two vertebrae in thespinal column. In one embodiment, the cages are positioned in a side byside relation to form a rigid transverse strut between adjacentvertebrae.

[0028] It is an object of the present invention to provide an improvedprosthetic implant for insertion between two vertebrae.

[0029] It is another object of the present invention is to provide aprosthetic implant which better emulates the space between thevertebrae.

[0030] Yet another object of the present invention to provide aprosthetic implant which includes one or more ridges to help secure theprosthetic implant in position between the vertebrae.

[0031] It is yet another object of the present invention to provide aprosthetic implant which is used in a side by side relation to form arigid transverse strut between adjacent vertebrae.

[0032] It is still yet another object of the present invention toprovide a prosthetic implant which provides improved spinal supportfixation and methodology which provides stability between adjacentvertebrae and the shape will facilitate in securing the prostheticimplant between the vertebrae.

[0033] Another object of the present invention is to provide anapparatus which will aid in the positioning of the prosthetic implantbetween the vertebrae.

[0034] Still yet another object of the present invention is to provide aprosthetic implant which has one or more openings that can receivepacking material to facilitate in the fusion of two adjacentlypositioned vertebrae.

[0035] A further object of the present invention is to provide aprosthetic implant which can be easily and efficiently positionedbetween two vertebrae and which reduces the failure rate of prostheticimplants between the vertebrae.

[0036] It is another object of the present invention to provide aprosthetic implant which includes one or more sloped surfaces tofacilitate in the insertion of the prosthetic implant between theadjacently positioned vertebrae and to better match the shape of theprosthetic implant to the space between the adjacently positionedvertebrae.

[0037] It is still another object of the present invention to provide aprosthetic implant which includes surfaces that reduce pinching with thespinal cord and other body parts closely adjacent to the prostheticimplant.

[0038] It is another object of the present invention to provide aprosthetic implant that is made of a biologically compatible material.

[0039] It is another object of the present invention to provide aprosthetic implant that is made of and/or coated with a radiolucentmaterial.

[0040] It is another object of the present invention to provide aprosthetic implant that is made of a material which closely approximatesthe elasticity of the vertebra.

[0041] These and other objects of the invention will become apparent tothose skilled in the art upon reading and understanding the followingdetailed description of preferred embodiments taken together with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention may take physical form in certain parts andarrangement of parts, preferred embodiments of which will be describedin detail and illustrated in the accompanying drawings which form a parthereof and wherein:

[0043]FIG. 1 is a top plan view of the prosthetic implant of the presentinvention;

[0044]FIG. 2 is a prospective view of the prosthetic implant of thepresent invention;

[0045]FIG. 3 is a side elevation view of the prosthetic implant of thepresent invention;

[0046]FIG. 3A is an enlarged view of an alternate ridge configuration inthe top wall of the prosthetic implant of FIG. 3;

[0047]FIG. 4 is prospective view of another embodiment of the prostheticimplant of the present invention which illustrates the dual sloping ofthe top and bottom walls of the prosthetic implant;

[0048]FIG. 4A is a rear end view of the prosthetic implant in FIG. 4;

[0049]FIG. 5 is a side elevation view of a spinal column which includesthe prosthetic implant of the present invention positioned between twoadjacently positioned vertebrae; and

[0050]FIG. 6 is a posterior elevation view of a portion of FIG. 5illustrating two adjacently positioned prosthetic implants positionedbetween two spinal vertebrae.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0051] Referring to the drawings, wherein the showings are for thepurpose of illustrating the preferred embodiment of the invention onlyand not for the purpose of limiting same, FIGS. 1-3 illustrate aprosthetic device or implant 10 which is designed to be inserted in anintervertebral disk space between two vertebrae of the spinal column.Prosthetic implant 10 is illustrated as being a cage-like structure 12having a top wall 20, a bottom wall 30, a front end wall 40, a back endwall 50, a first side wall 60, and a back side wall 70. As bestillustrated in FIGS. 1 and 2, the top wall 20 includes a plurality ofridge structures 80 which are positioned along the longitudinal lengthof prosthetic implant 10. As illustrated in FIG. 3, ridge structures 80are also included on bottom wall 30. The ridge structures can be cutinto the top and bottom walls and/or be formed by a molding process. Theridge structures are designed to bite into and/or readily form a rigidcontact with the underside surface of the vertebrae so as to secure theprosthetic implant between the vertebrae and reduce the movement of theprosthetic implant of the vertebrae after the prosthetic implant hasbeen properly positioned between the vertebrae.

[0052] Referring to FIGS. 1 and 2, ridge structures 80 are shown to bespaced from the peripheral edge 22 of top wall 20. This same spacing ofthe ridges also exists on the bottom wall. Top wall 20 is also shown toinclude an opening 100. Many different ridge configurations can be usedon the top and bottom walls of cage 10. Two preferable configurationsare illustrated in FIGS. 1 and 3A. In FIG. 1, the ridge structures aregroove type ridges that are oriented along the lateral axis of cage 12.The ridge structures have two sides that are similar in length. In onearrangement, the height of the ridge structure from valley to peak isabout 0.01 to 0.05 inch, and the spacing between ridge peaks is about0.01 to 0.12 inch. As can be appreciated, these dimensions of the ridgestructures can be modified for use in a particular application.

[0053] Referring now to FIG. 3A, an alternative configuration of theridge structure is shown. Ridge structures 80 are generally diamondshaped structures wherein each ridge structure has four walls. The walls82 of the diamond shaped ridge structure are generally the same size andshape. In one arrangement, the height of the ridge structure from valleyto peak is about 0.01 to 0.05 inch, and the spacing between ridge peaksis about 0.01 to 0.12 inch. As can be appreciated, these dimensions ofthe ridge structures can be modified for use in a particularapplication.

[0054] The ridge structures can be oriented in the top and/or bottomwall to facilitate in the stacking or two or more prosthetic implants.

[0055] Referring to FIGS. 1 and 4, the top and bottom wall of cage 12includes an openings 100, 120. Openings 100, 120 are illustrated asbeing semi-oval shaped; however, other opening shapes can be used. Thesize of the opening is selected so packing materials 300 can be insertedin the openings. In one desired arrangement, the size of openings 100,120 are maximized to increase the volume of packing materials that canbe inserted into the cage without adversely affecting the structuralintegrity of the cage. As illustrated in FIGS. 1 and 4, openings 100 and120 have a similar shape and size; however, other shapes and sizes ofthe openings can be used. The openings are shown to have a peripheraledge spaced at a generally uniform distance from the peripheral edge ofthe top and bottom wall. In one desired arrangement, the spacing of theperipheral edge of the opening from the peripheral edge of the top andbottom walls is about 0.05 to 0.25 inch; however, other spacings can beused based upon the material and size of the cage.

[0056] Referring now to FIGS. 1, 2 and 4, cage 12 includes a cavity 130.Cavity 130 is shown to be in communication with opening 100, 120 in thetop and bottom walls of cage 12. The cavity is designed to increase theamount of packing material that can be inserted in the cage. The packingmaterial 300 includes, but is not limited to, medicine, tissue, cells,and the like. In one desired arrangement, the packing material isselected to facilitate in the growth of bone between the two vertebraein which the prosthetic implant is inserted therebetween.

[0057] Referring now to FIG. 2, the first side wall 60 has an arcuate orcurvilinear shape along the longitudinal length of the wall. The arcuateshape of the first side wall is selected to more closely anatomicallymatch the intervertebral disk space. Second side wall 70 is illustratedas having a substantially straight or planar face. When prostheticimplant 10 is positioned in the intervertebral disk space, second sidewall 70 is positioned closely adjacent to the spinal cord and first sidewall 60 is positioned adjacent the outer edge of the vertebrae. Thecurvilinear first side wall and the substantially planar or straightsecond side wall are designed to more closely match the intervertebraldisk space and to increase the surface area of contact with thevertebrae to assist in reducing slippage and to increase the successrate of the fusion between two vertebrae. As can be appreciated, theshape of the arcuate surface of first side wall 60 can be adjusteddepending on the vertebrae in which the prosthetic implant is to beinserted therebetween. As also can be appreciated, second side wall 70may also be shaped to include non-planar surfaces to further facilitatein the maximization of contact of the surfaces of the prosthetic implantto the underside surfaces of the vertebrae. In one desired embodiment,the planar second side wall has a length of about 0.5 to 1.2 inch and aheight of about 0.2 to 0.8 inch. In another desired embodiment, theradius of curvature of the first side wall is about 0.3 to 0.9 inch anda height of about 0.1 to 0.75 inch. As can be appreciated, the size andconfiguration of the side wall can take on other dimensions andconfigurations depending on the use of the prosthetic implant.

[0058] Referring again to FIG. 2, first side wall 60 and second sidewall 70 include openings 140 which communicate with inner cavity 130. Aswith openings 100 and 120 in the top and bottom walls, openings 140 aredesigned to receiving packing material 300 and to allow for blood flowbetween the packing material within the cavity 130 and the surroundingregions of the vertebrae. Openings 140 are illustrated as being diamondshaped; however, other shapes can be used. The side walls are alsoillustrated as each including two openings 140; however, more or lessopenings can be included in the side walls. In one desire embodiment,oval or diamond shaped openings are used in the side walls to maximizethe opening size without adversely affecting the structural integrity ofthe cage.

[0059] Referring again to FIG. 2, the side walls include an instrumentopening 150 which is designed to receive an instrument to enable theprosthetic device to be inserted in the intervertebral disk space innumber of different approaches. In one desired embodiment, theprosthetic implant includes a plurality of instrument opening 150 toenable the prosthetic implant to be inserted in the intervertebral diskspace from an anterior, posterior, lateral, and/or lateralscopicapproach to the vertebrae. In another desired embodiment, the instrumentopening 150 is a threaded opening which receives a threaded instrument.The threaded opening allows an instrument to be simply secured to and/orremoved from the prosthetic implant 10. The instrument opening 150 canalso be used to secure pedicle screws to the prosthetic implant so as tofacilitate attachment to a rod or plate stabilization system to theprosthetic implant.

[0060] Referring now to FIGS. 2 and 4, front and back end walls 40, 50include an instrument opening 160. The configuration and function ofinstrument opening 160 is the same as instrument opening 150 in thefirst and second walls of cage 12.

[0061] Referring now to FIG. 2, the peripheral edges of the walls of thecage are rounded off or contoured. The rounded off edges 200 aredesigned to minimize or eliminate sharp edges on the cage to reduceand/or eliminate pinching of the nerves, and to facilitate in thepositioning of the cage in the intervertebral disk space.

[0062] Referring now to FIG. 3, the top and bottom walls of the cage areinclined. Top wall 20 and bottom wall 30 are shown to slope downwardlyfrom back end wall 50 to front end wall 40. The angle of incline isshown to be generally uniform throughout the longitudinal length of theprosthetic implant. The degree of inclination of both the top wall andbottom wall of the prosthetic implant is substantially the same. Due tothe sloping surfaces of the top and bottom wall, the back end wall 50 isshown to have a higher height than front wall 40. In one desiredembodiment, the height of the back end wall is about 0.2 to 0.8 inch,the height of the front side wall is about 0.1 to 0.75 inch, and theangle of slope of the top and bottom wall from the back to front endwall is about 0.5 to 20 degrees.

[0063] Referring now to FIGS. 3, 4 and 4A, the top and bottom walls ofcage 12 are inclined from the second side wall to the first side wall.In one desired embodiment, the degree of inclination of the top andbottom wall from the second side wall to the first side wall issubstantially uniform. Due to the incline of the top and bottom wall,the second side wall has a higher height than the first side wall. Inanother desired embodiment, the angle of slope of the top and bottomwall from the back to front end wall is about 0.5 to 20 degrees.

[0064] Referring now to FIGS. 5 and 6, the lower portion of the humanvertebrae column 210 is illustrated. FIG. 5 illustrates five lowervertebrae of the spinal column. Vertebrae 220 and 230 are separated byand supported on the prosthetic implant 10 of the present invention. Theremaining vertebrae are illustrated as being supported on and separatelyby intervertebral disk 250 which maintains a space 260 between theadjoining vertebrae. The damaged portions of intervertebral disk 250have been removed from between vertebrae 220 and 230 prior to prostheticimplant 10 being inserted therebetween. As shown in FIG. 6, twoprosthetic implants 10 are positioned side by side between vertebrae 220and 230.

[0065] As an overview of one embodiment of the invention, the prostheticimplant is a solid structure of a cage having one or more cavities. Theimplant is to be inserted into the vertebral column during surgery toprovide load bearing support for the vertebrae in the vertebral column.The implant is shaped to provide a slope laterally so that the mediumaspect closest to the spinal column is higher than the lateral aspect.The implant has one or more openings in the cage to allow for packingmaterials not rejected by the human body. These packing materialsinclude, but are not limited to, autologous bone, donated human bonematerial, other mammalian materials, and/or other natural or artificialmaterials. The cage is sloped from the anterior to the posterior. Thecage has rounded edges to reduce spinal pinching. The top and bottomwalls of the cage include ridges or grooves that are carved into the topand bottom walls to facilitate in the fixation and anchoring of the cagebetween two vertebrae. The ridges can have several configurations, onebeing a cross hatched or teeth design which form diamond bumps orpyramids. The cage has one or more arcuate or curvilinear sides thatforms an ovoid shaped cage or a double domed disk configuration.

[0066] In the most common applications, two prosthetic implants will beutilized and inserted in the intervertebral disk space, one on each sideof the lateral sides of the spinal column. The prosthetic devices willreplace a damaged or injured disk that is partially or wholly removedduring a surgical procedure. During the surgical procedure, the implantswill be inserted and fixed in a location to avoid intrusion into thespinal cord area while at the same time avoiding extending outside thevertebral column. This placement of the prosthetic implants is optimizedby utilizing the prosthetic implant of the present invention.

[0067] Some advantages and improvements of the prosthetic implant overprior art implants are:

[0068] The corners of the implant are rounded.

[0069] The top wall of the implant slopes from one side wall to anotherside wall.

[0070] The bottom wall of the implant slopes from one side wall toanother side wall.

[0071] The top wall of the implant slopes from one end wall to anotherend wall.

[0072] The bottom wall of the implant slopes from one end wall toanother end wall.

[0073] The implant includes larger and/or more openings to facilitate inthe packing of the implant with bone and/or bone growth promoters.

[0074] The top and/or bottom surfaces of the implant include ridgedsurfaces having a diamond shaped design for better bone anchoring.

[0075] The walls of the implant include one or more threaded holes toenable the implant to be inserted from the anterior, posterior, lateral,or laproscopic approach during surgery.

[0076] The implant is designed to receive interference screws and/orstints used to inhibit the migration of the implant within theintervertebral disk space.

[0077] The implant can be made of a variety of materials such as choppedcarbon fiber/polymer, other polymers, various metals, memory metals,ceramics, bone, bio-resorbables, and/or composites.

[0078] The implant can be made of a memory metal that can be expandedafter being inserted in the intervertebral disk space. The cage can bedesigned to be expanded “in vivo.”

[0079] The implant can be used with a modular component that can beattached and assembled between two implants to create a construct (ALIFtype) cage.

[0080] The implant can be stacked upon one another to form a corpectomycage having various shapes and sizes.

[0081] The implant is designed to accept insertion of machine-threadedpedicle screws so as to facilitate attachment to a rod or platestabilization system.

[0082] The invention has been described with reference to the preferredembodiments. These and other modifications of the preferred embodimentsas well as other embodiments of the invention will be obvious from thedisclosure herein, whereby the foregoing descriptive matter is to beinterpreted merely as illustrative of the invention and not as alimitation. It is intended to include all such modifications andalterations in so far as they come within the scope of the appendedclaims.

I claim:
 1. A prosthetic implant to form a rigid structure betweenadjoining vertebrae in a spinal column, comprising a cage defined bytop, bottom, front end, back end, first side and second side walls, saidfirst and second side walls extending substantially along a longitudinalaxis of said cage, said front and back end walls having a width lessthan the length of said first side and said second side walls, said topwall and said bottom wall positionable between and engageable with asurface of an adjacent vertebrae, said first side wall having an arcuatesurface.
 2. The prosthetic implant as defined in claim 1 , wherein saidtop wall includes at least one ridge to engage a surface of an adjacentvertebrae.
 3. The prosthetic implant as defined in claim 1 , whereinsaid bottom wall includes at least one ridge to engage a surface of anadjacent vertebrae.
 4. The prosthetic implant as defined in claim 2 ,wherein said top wall includes a plurality of ridges.
 5. The prostheticimplant as defined in claim 2 , wherein at least one of said ridgeincludes a plurality of teeth.
 6. The prosthetic implant as defined inclaim 2 , wherein said ridge being spaced from a peripheral edge of saidfirst or second side wall.
 7. The prosthetic implant as defined in claim1 , wherein said top wall including an opening to receive packingmaterial, said packing material including a material selected from thegroup consisting of medicine, human tissue, animal tissue, synthetictissue, human cells, animal cells, synthetic cells, and combinationsthereof.
 8. The prosthetic implant as defined in claim 1 , wherein saidbottom wall including an opening to receive packing material, saidpacking material including a material selected from the group consistingof medicine, human tissue, animal tissue, synthetic tissue, human cells,animal cells, synthetic cells, and combinations thereof.
 9. Theprosthetic implant as defined in claim 1 , wherein said top wall havinga peripheral edge, at least a portion of said peripheral edge beingcontoured so as not to be sharp.
 10. The prosthetic implant as definedin claim 1 , wherein said bottom wall having a peripheral edge, at leasta portion of said peripheral edge being contoured so as not to be sharp.11. The prosthetic implant as defined in claim 1 , wherein said top wallbeing inclined from said second side wall to said first side wall. 12.The prosthetic implant as defined in claim 1 , wherein said bottom wallbeing inclined from said second side wall to said first side wall. 13.The prosthetic implant as defined in claim 1 , wherein said top wallbeing inclined from said back end wall to said front end wall.
 14. Theprosthetic implant as defined in claim 1 , wherein said bottom wallbeing inclined from said back end wall to said front end wall.
 15. Theprosthetic implant as defined in claim 1 , wherein said back side wallbeing higher than said front side wall.
 16. The prosthetic implant asdefined in claim 1 , wherein said first side wall including an openingto receive packing material, said packing material including a materialselected from the group consisting of medicine, human tissue, animaltissue, synthetic tissue, human cells, animal cells, synthetic cells,and combinations thereof.
 17. The prosthetic implant as defined in claim1 , wherein said second side wall including an opening to receivepacking material, said packing material including a material selectedfrom the group consisting of medicine, human tissue, animal tissue,blood, stem cells and combinations thereof.
 18. The prosthetic implantas defined in claim 1 , wherein at least one of said front end wall,said back end wall, said first side wall and said second side wallincluding an opening, said opening adapted to receive an instrument toguide said prosthetic implant between adjoining vertebrae in a spinalcolumn, to receive an implant to secure said cage in position relativeto said vertebrae, and combinations thereof.
 19. The prosthetic implantas defined in claim 1 , wherein said first side wall being asubstantially uniform arcuate surface.
 20. A prosthetic implant to forma rigid structure between adjoining vertebrae in a spinal column,comprising a cage defined by top, bottom, front end, back end, firstside and second side walls, said first and second side wall extendingsubstantially along a longitudinal axis of said cage, said front andback end walls having a width that is less than the length of said firstside and said second side walls, said top wall and said bottom wallpositionable between and engageable with a surface of an adjacentvertebrae, at least one of said top and bottom walls being inclined fromsaid second side wall to said first side wall.
 21. The prostheticimplant as defined in claim 20 , wherein both said top and bottom wallsbeing inclined from said second side wall to said first side wall. 22.The prosthetic implant as defined in claim 20 , wherein said second sidewall being higher that said first side wall.
 23. The prosthetic implantas defined in claim 20 , wherein said top and bottom walls include aplurality of ridges to engage a surface of an adjacent vertebrae. 24.The prosthetic implant as defined in claim 23 , wherein said ridgesinclude a plurality of teeth.
 25. The prosthetic implant as defined inclaim 20 , wherein said ridges are spaced from a peripheral edge of saidfirst and second side wall.
 26. The prosthetic implant as defined inclaim 20 , wherein said top and bottom walls include an opening toreceive packing material, said packing material including a materialselected from the group consisting of medicine, human tissue, animaltissue, synthetic tissue, human cells, animal cells, synthetic cells,and combinations thereof.
 27. The prosthetic implant as defined in claim20 , wherein said top, bottom, front end, back end, first side andsecond side walls each having a peripheral edge, at least a portion ofsaid peripheral edges of each of said walls being contoured so as not tobe sharp.
 28. The prosthetic implant as defined in claim 20 , whereinsaid top and bottom walls are inclined from said back end wall to saidfront end wall.
 29. The prosthetic implant as defined in claim 20 ,wherein said back side wall being higher than said front side wall. 30.The prosthetic implant as defined in claim 20 , wherein at least one ofsaid front end wall, said back end wall, said first side wall and saidsecond side wall including an opening, said opening adapted to receivean instrument to guide said prosthetic implant between adjoiningvertebrae in a spinal column, to receive an implant to secure said cagein position relative to said vertebrae, and combinations thereof. 31.The prosthetic implant as defined in claim 30 , including a cavitywithin said cage, said cavity in communication with said at least one ofsaid opening in at least one of said front end, said back end, saidfirst side and said second side walls, said cavity adapted to receivepacking material that includes a material selected from the groupconsisting of medicine, human tissue, animal tissue, synthetic tissue,human cells, animal cells, synthetic cells, and combinations thereof.32. The prosthetic implant as defined in claim 20 , wherein said frontside wall having a substantially uniform arcuate surface.